This invention relates to a plate-like rotary body such as a circular saw with vibration-suppressing characteristics which may be used in a wide range of applications and a method of manufacturing such a body.
A circular saw tends to develop Karman vortices on the backside of cutting edges and to cause vibrations when it idles. When the rotational speed of the saw corresponds to one of its characteristic frequencies, unpleasant metallic noise developed by it becomes particularly large. During a cutting operation, the saw begins to vibrate because of the alternate cutting load applied on the cutting edges, resulting not only in large noise but also in a resonance phenomenon with the characteristic frequency of the rotary body. In view of this situation, various vibration-suppressing means have been considered. Japanese patent publication Tokko No. 53-16952 disclosed circular saws, as shown in FIGS. 13 and 14, with a small notch 21 formed from the bottom of its tooth section towards the center. A curved slit or slits 23 are formed to connect the deep end of this notch 21 with a circular hole or holes 22 drilled in the saw plate such that vibrations are suppressed by the close contact between the parts on both sides of the curved slit or slits. Under severe conditions of use, however, such a notch frequently causes deformation in the saw plate, rendering the saw unusable. Japanese patent publication Tokkai No. 59-134616 disclosed, as shown in FIG. 15, a circular saw with very narrow slits in radical directions to suppress vibrations but their effects are not totally satisfactory.